As a positive reinforcement trainer that uses food in training, I often have people ask me "when can I stop giving him treats?" My answer is "never...and why would you want to?" Now, to clarify that a bit further, what I am really saying is, reinforcing behavior you like from your dog, should never stop. I really like my job but if I stopped being paid for it I would probably stop doing it on a regular basis, unless I really wanted to. See how that can translate to your dog?
In my classes and private lessons I teach people to train their dogs using the biggest motivator around; food. I also teach them that there are other types of reinforcers that can replace food for every day behaviors, ie: sit doesn't always have to mean a cookie, sit can mean the Frisbee gets thrown or he gets lots of lavish attention. But those reinforcers are usually used as back ups to the tried and true food reward when new behaviors are being taught. For a dog, food talks!
I like to talk about making deposits into my dogs' reinforcement account. What that means is I pay him heavily and on a consistent basis for behaviors I expect him to perform, such as coming when called. If I pay him every single time for coming when called, with food, attention or play, the one time I REALLY need that behavior to occur and I don't have any major reinforcer with me, I won't have damaged the behavior. Think of it as a checking account, if you are constantly in the black then you feel pretty secure knowing you have the ability to make a withdrawal when an emergency hits, without decimating the account altogether. Conversely, if you are constantly making more withdrawals than deposits, pretty soon the account will run dry and stop working for you! Your dog will work the same way, if a behavior stops working for him ie: being reinforced, it will die off or become very unreliable and for a behavior like coming when called, that can be extremely dangerous.
So the goal in training your dog should not be to stop reinforcing the behaviors we like; it should be to get to the point where the frequency and type of reinforcers can change to better suit everyday life. If you want consistent, long term success in the behaviors you teach your dog they need to be well reinforced on a consistent basis, even into adulthood. Remember, any behavior that is reinforced will be repeated. Figure out what behavior you want your dog to repeat on a regular basis and reinforce it!!